JP7060443B2 - A method for producing an oil-in-water emulsion and an oil-in-water emulsion. - Google Patents

Description

The present invention relates to an oil-in-water emulsion and a method for producing an oil-in-water emulsion, and more particularly to a method for producing an oil-in-water emulsion and an oil-in-water emulsion in which stability is ensured.

An aqueous dispersion in which inorganic solid particles such as silica and titanium oxide are dispersed in water to be in an emulsified state, a suspended state, etc. has been conventionally known and is widely used as a rheology control agent and a compounding agent for cosmetics. In the aqueous dispersion of these inorganic particles, the stability that the inorganic particles do not settle for a long time in the dispersed state and the local bias in the dispersed aqueous dispersion are due to the fact that the inorganic particles are not dissolved in water. Uniformity in the sense that is not occurring is important.
Especially when fumed silica is used as the inorganic particles, in the case of hydrophobic silica, the aqueous dispersion is imparted with thickening and thixotropy, while the aqueous dispersion itself is excessively thickened and the hydrophobic silica particles settle. There was instability such as. On the other hand, in the case of hydrophilic silica, the hydrophilic silica dissolves in water and stability can be ensured in that sense, but it is not suitable when used in applications requiring high viscosity as an aqueous dispersion. ..
As described above, although the required characteristics vary depending on the use as an aqueous dispersion, it is technically difficult to achieve both the required characteristics and the stability and uniformity of the aqueous dispersion.

In this regard, Patent Document 1 pays attention to the contact angle of silica in the bulk state as an aqueous dispersion when the inorganic particles are silica, and optimizes the contact angle in the aqueous dispersion of silica for a long time. It is disclosed to improve the stability in the sense of suppressing the sedimentation of silica over time.
However, there is no disclosure regarding not only the stability in the dispersed state but also the point of ensuring the uniformity in the dispersed state, let alone the compatibility between the characteristics required for the aqueous dispersion and the stability and uniformity of the aqueous dispersion. , Not even suggested.

On the other hand, in an emulsion which is an emulsified state of a solid phase or a liquid phase and a liquid phase, which is one aspect of a dispersion, a technique for forming an emulsified state using a surfactant has been conventionally known, and the emulsion. Similarly to the aqueous dispersion, stability in an emulsified state is important in the sense that the solid phase or the liquid phase and the liquid phase do not separate with the passage of time.

In Patent Document 2, in particular, as a pickering emulsion using inorganic particles as a substitute for a surfactant, those in which various oily components are emulsified with titanium oxide particles are used for cosmetics and the like.
Further, Patent Document 3 also knows a pickering emulsion in which silicone oil and other silicone substances are emulsified with silica particles.
As an oil-in-water emulsion, such a pickering emulsion is composed of composite particles composed of oil droplets constituting a core and inorganic particles existing on the surface of the oil droplets at the interface between the oil phase and the aqueous phase. It takes the form of being in an emulsified state in the aqueous phase.
By forming an emulsion without using an organic surfactant, these eliminate the harmful effects of the organic surfactant, which is harmful to the environment, and provide silica as a functional agent in an aqueous system rather than as particles. As an oil-in-water emulsion, it is expected to be used in various applications such as pharmaceuticals, foodstuffs, and antifoaming agents.
In such a pickering emulsion, in Non-Patent Document 1, Non-Patent Document 2 and Non-Patent Document 3, inorganic particles existing at the interface as inorganic particles as an alternative to a surfactant for ensuring the stability of the pickering emulsion. It has been pointed out that the hydrophobic-hydrophilic balance of is important.
However, the conventional pickering emulsion has the following technical problems.

First, it is insufficient to secure the stability in the emulsified state in the sense that the solid phase or the liquid phase and the liquid phase do not separate with the passage of time.
More specifically, in Non-Patent Document 1 and Non-Patent Document 2, as a pickling emulsion model, a simple model in which spherical particles are present at the interface between a liquid phase (for example, an aqueous phase) and a liquid phase (for example, an oil phase). When forming a pickering emulsion, the timing of adding inorganic particles in the relationship between the aqueous phase and the liquid phase, the shear rate for emulsification, and the shear time are the characteristics of the emulsion. No attention has been paid to how it affects the emulsion, and therefore the factors and mechanisms governing the stability of the emulsion have not been elucidated.

In particular, when silica is used as the inorganic particles, how the primary and secondary aggregates formed due to the cohesiveness of silica affect the hydrophobic-hydrophilic balance. Is not mentioned.
In this regard, in Non-Patent Document 3, hydrophobic silica is used as the inorganic particles, and a hydrophilic polymer surfactant is adsorbed on the surface of the hydrophobic silica to adjust the hydrophobic-hydrophilic balance. Attempts have been made to change the properties of the emulsion.
However, in Non-Patent Document 3, based on hydrophobic silica as inorganic particles, only a hydrophilic polymer surfactant is adsorbed, the core oil phase is also one type, and the type of oil agent to be emulsified is There is a problem of limitation, and even if the hydrophobic-hydrophilic balance affects the properties of the emulsion, the method of adjusting the hydrophobic-hydrophilic balance is complicated and costly, and the emulsion is commercialized. It is not established as a product design method when doing so.
Conventionally, as a method for designing a pickering emulsion using such industrial silica particles, silica is hydrophobic at the raw material stage in order to emulsify the oil by partially hydrophobizing the silanol groups on the surface of silica. It was only a pretreatment of the degree of conversion, and it was unclear what design parameters should be focused on in order to produce a stabilized emulsion at an industrially practical level.

Secondly, the composite particle group that is isolated and produced by removing water after the pickering emulsion is formed, for example, the composite particles existing on the surface (intersection) of the oil droplets in which the silica particles are the core, are inorganic particles. Where certain silica particles can be firmly adhered to the core surface in a manner that covers the surface of oil droplets, the silica particles as a functional agent and the core as another functional agent are applied separately to each other. Although it is expected to be versatile as a composite particle group, such as when it is more advantageous to apply it as a composite particle than when it is applied, the problem of variation between composite particle groups is examined. Has not been done.
More specifically, composite particles have, as specifications, particle size, coating layer thickness, coverage and embedding degree (contact angle) of silica particles in the core surface, and particle size, coating layer thickness and coverage. , The degree of embedding of silica particles in the core surface is deeply related to the degree of adhesion between the silica particles and the core, and such specifications cause variations among the composite particle groups. Therefore, it becomes difficult to provide reliable products.

Thirdly, when forming a pickering emulsion, attention has been conventionally paid to adjusting the particle diameter, coating layer thickness, coating degree, and embedding degree (contact angle) as specifications of composite particles according to the application. Not.
More specifically, for example, in the case of cosmetic applications, composite particles having a core made of silicone rubber particles are often adopted, but even if the particle size and the coating layer thickness affect the usability, the particle size and the particle size and the thickness of the coating layer are affected. How to adjust the coating layer thickness has not been examined.
More specifically, if the entire composite particle is soft, the adhesion to the skin after the composite particle is applied is excellent, but the composite particle is deformed at the time of application, the adhesion area to the skin is increased, and the space between the particles is increased. Since the frictional resistance increases, the extensibility of the composite particles to the skin decreases. By softening the rubber particles that are the core, while hardening the silica coating layer that constitutes the outer shell, such extensibility is achieved. There is a demand for technology to secure it.

Related to the second and third points, fluorocarbon, which is a hydrocarbon in which the hydrogen atom is partially replaced with a fluorine atom, is an organopoly having normal stability, heat resistance, water resistance, oil resistance, and water repellency. The structure of fluorocarbons in the skeleton of organopolysiloxanes is known to have characteristic properties not found in ordinary organopolysiloxanes, such as better than siloxanes such as dimethylpolysiloxanes and oil repellency. By introducing (fluorine-containing organopolysiloxane), in various forms such as oil, rubber, and resin, bulk, solution, dispersed liquid (or suspension), film, granular (or powder). Although various shapes such as these are expected to be used for various purposes in order to exhibit their excellent characteristics, it is extremely difficult to develop the applications in the form of granules or powders at present.
The reason is that due to the super water repellency or super oil repellency of the fluorine-containing organopolysiloxane, it is difficult to form a solution or dispersion of water or an organic solvent, a suspension, and the solvent in these solutions. Since it cannot be granulated or powdered by evaporating, the only alternative is to grind it from the form of rubber or resin, so the shape of the granules or powder is irregular and the size varies. Was also big.

In this regard, in Patent Document 4, the applicant of the present invention disperses in water by forming high-level aggregates by non-chemical bonds between lower aggregates of the inorganic particle group, such as fumed silica particles. In an aqueous dispersion and an oil-in-water pickering emulsion pickering in which oil is added based on such an aqueous dispersion, a mechanism of stability adjustment by exchange (rearrangement) or movement (orientation) at the aggregate level is provided. I'm finding out.
More specifically, in an aqueous dispersion in which lower aggregates of the inorganic particle group form high-level aggregates by non-chemical bonds and are dispersed in water, exchange (rearrangement) at the aggregate level. ) Or migration (orientation) produces hydrophilic-rich aggregates, hydrophobic-rich aggregates, and intermediate aggregates (self-micellar aggregates), where self-micellar aggregates are aqueous dispersions, and such. We have discovered that it is important for the stability of oil-in-water pickering emulsions that add oil based on an aqueous dispersion.

However, the relationship between the network structure formed by the high agglomeration of fumed silica particles and the stability of oil-in-water pickering emulsions, especially in hydrophilic rich agglomerates, hydrophobic rich agglomerates, and self-micellar agglomerates. It does not matter how forming a network structure between the same or different aggregates affects the stability of an oil-in-water pickering emulsion, in particular it is superhydrophobic or superoil repellent. No studies have been made on whether an oil-in-water pickering emulsion containing a fluorine-containing organopolysiloxane as an oil can be formed in the first place, and the conditions for forming the emulsion.
It was a common general knowledge of those skilled in the art at that time that it was not expected that an oil-in-water pickering emulsion containing a fluorine-containing organopolysiloxane having superhydrophobicity or superhydrophobicity could be formed. Is shown.

Japanese Unexamined Patent Publication No. 2004-203735 Japanese Unexamined Patent Publication No. 2000-95632 Japanese Unexamined Patent Publication No. 2008-31487 Patent No. 631234

J. Jpn. Soc. Color Mater. , 89 (6), 203 (2016) J. Chem. Phys. , 124, 241104 (2006) 2010 Master's Thesis by Tomoyuki Suzuki, Department of Molecular Materials Engineering, Graduate School of Engineering, Mie University

In view of the above technical problems, an object of the present invention is to provide an oil-in-water emulsion and a method for producing an oil-in-water emulsion that ensure stability.
In view of the above technical problems, an object of the present invention is to provide a method for forming granules or powders using a fluorine-containing organopolysiloxane, which is stylized and has a small variation in size.

As a result of diligent studies, the present inventors have found that when the fumed silica particles form a network due to the high agglomeration of the fumed silica particles, the space is not a planar structure but a three-dimensional interior. The total number of moles of surface hydrophilic groups in each of the fumed silica particle groups over the fumed silica particle group / the fume, depending on the agglomeration of the fumed silica particles. By setting the total molar ratio, which is the total number of moles of the surface hydrophobic group in each of the dosilica particle groups, which is the total number of moles over the fumed silica particle group, to be equal to or higher than the predetermined lower limit value and / or to the predetermined upper limit value or less. We have found that which of the self-micellar aggregates, hydrophobic rich aggregates, and hydrophilic rich aggregates is proactively produced is determined, and an aqueous dispersion according to the purpose such as thickening and imparting thixotropic properties is available. I found that I could provide it. It was also found that the self-micellar aggregates are particularly stable and have excellent uniformity.
When the inorganic particles are fumed silica, if the ratio of the total number of moles is set in the range of 20/80 to 80/20 at the raw material silica stage, a self-micellar aggregate-rich aqueous dispersion can be obtained. I found out what I could do.

Further, in order to obtain an oil-in-water emulsion (pickering emulsion) by coating an oil droplet with a self-micellar aqueous dispersion of fumed silica particles, a shear rate of a predetermined value or higher is mainly obtained at the stage of the aqueous dispersion. By promoting the rearrangement of the primary aggregates among the secondary aggregates and / or the orientation of the primary aggregates in the secondary aggregates, the variation in the degree of hydrophobicity among the composite particles can be reduced. , Found that a more stable and uniform oil-in-water emulsion is produced.

The present invention has been made based on these findings.
That is, the method for producing and designing the oil-in-water emulsion and the oil-in-water emulsion of the present invention are as follows.
(1) A group of fumed silica particles in which lower aggregates of the group of fumed silica particles form high-level aggregates by non-chemical bonds, and form a network-like surrounding structure containing oil inside. , Featuring an oil-in-water emulsion,
(2) In the network-like surrounding structure, the high-density portion of the lower hydrophilicity-rich aggregate is in contact with the aqueous phase, and the high-density portion of the hydrophobic-rich lower aggregate is in contact with another hydrophobic-rich lower aggregate. The oil-in-water emulsion according to claim 1, which comprises a self-micellar aggregate that contacts and forms a space inside.
(3) The oil-in-water emulsion according to claim 2, wherein in the self-micellar aggregate, the lower aggregates form a network-like structure.
(4) A group of fumed silica particles having a secondary aggregation level by mixing a hydrophobic rich silica raw material obtained by hydrophobizing the surface silanol groups and a hydrophilic rich silica raw material having residual surface silanol groups at a predetermined ratio. And the stage of preparing
By adding the prepared fumed silica particle group at the secondary aggregation level to water and shearing at a shear rate of a predetermined value or higher, the lower aggregates of the fumed silica particle group are highly coagulated by non-chemical bonding. At the stage of forming an aqueous dispersion containing a network-like surrounding structure having a space formed inside, which is a group of fumed silica particles forming an aggregate.
It has a step of adding an oil component to form an emulsion in the generated aqueous dispersion.
A method for producing an oil-in-water emulsion, which comprises a composite particle group in a form containing oil in a network-like surrounding structure formed by a fumed silica particle group at a secondary aggregation level.
(5) Prior to the formation stage of the aqueous dispersion, the fumed silica particle group at the secondary aggregation level and the organic surfactant are blended in a predetermined blending ratio so as to adjust the morphology of the network-like surrounding structure. The method for producing an oil-in-water emulsion according to claim 4, which has a step.
(6) In the network-like surrounding structure, the high-density portion of the lower hydrophilicity-rich aggregate is in contact with the aqueous phase, and the high-density portion of the hydrophobic-rich lower aggregate is in contact with another hydrophobic-rich lower aggregate. The method for producing an oil-in-water emulsion according to claim 4 or 5, which comprises a self-micellar aggregate that contacts and forms a space inside.
(7) The compounding step of the fumed silica particle group at the secondary aggregation level and the organic surfactant adjusts the adhesion of the self-micellar aggregate to the oil droplets surrounded by the self-micellar aggregate. The method for producing an oil-in-water emulsion according to claim 6, which comprises a step of determining a predetermined blending ratio, and (8) the preparation step of the fumed silica particle group at the secondary aggregation level are self-micellar aggregates. The total number of moles of surface hydrophilic groups in each of the fumed silica particle groups over the fumed silica particle group / the number of moles of surface hydrophobic groups in each of the fumed silica particle groups so as to adjust the ratio. The oil-in-water emulsion according to claim 6, further comprising a step of mixing the hydrophobic-rich silica raw material and the hydrophilic-rich silica raw material, with the total molar number ratio, which is the total number of moles over the fused silica particle group, as a predetermined range. It is a manufacturing method of.

That is, the method for forming granules or powders of the present invention is
(9) The oil content is an organopolysiloxane whose average composition is represented by the general formula (1).
R ¹ _a R ² _b SiO _{(4-ab) / 2} (1)
[In formula (1), R ¹ may be the same or different in the molecule, and is a substituted or unsubstituted saturated or unsaturated monovalent hydrocarbon group having 1 to 25 carbon atoms, substituted or unsubstituted. It is an aromatic group having 6 to 30 carbon atoms, a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms or a hydrogen atom, and R ² may be the same or different in the molecule and has 1 to 25 carbon atoms. Saturated or unsaturated monovalent hydrocarbon group, or an aromatic group having 6 to 30 carbon atoms, in which a hydrogen atom on at least one carbon is substituted with a fluorine atom, and b is not 0. Positive number, a + b is greater than or equal to 0.3 and less than 2.5]
Granules having a variation in particle size within a predetermined range by evaporating the aqueous phase by a spray-drying method using the oil-in-water emulsion produced by the method for producing an oil-in-water emulsion according to claim 6 or 7. A method for forming a granular material or powder, which further comprises a step of forming the product or powder, and (10) the oil content is an organopolysiloxane whose average composition is represented by the general formula (1). can be,
R ¹ _a R ² _b SiO _{(4-ab) / 2} (1)
[In formula (1), R ¹ may be the same or different in the molecule, and is a substituted or unsubstituted saturated or unsaturated monovalent hydrocarbon group having 1 to 25 carbon atoms, substituted or unsubstituted. It is an aromatic group having 6 to 30 carbon atoms, a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms or a hydrogen atom, and R ² may be the same or different in the molecule and has 1 to 25 carbon atoms. Saturated or unsaturated monovalent hydrocarbon group, or an aromatic group having 6 to 30 carbon atoms, in which a hydrogen atom on at least one carbon is substituted with a fluorine atom, and b is not 0. Positive number, a + b is greater than or equal to 0.3 and less than 2.5]
Using the oil-in-water emulsion produced by the method for producing an oil-in-water emulsion according to claim 6 or 7, the aqueous phase is evaporated by a spray-drying method to form fumed silica particles on the outer surface of the oil droplets. At the stage of forming a composite particle group in which the group firmly adheres,
When applying the composite particle group to the surface of the substrate, the granular material or powder is characterized by having a step of first applying the fumed silica particle group to the substrate and then applying the oil component to the substrate. It is a forming method.

Action of invention

According to the present invention, due to the high cohesiveness of the fumed silica particles at the stage of the aqueous dispersion, when the fumed silica particles form a network, the space is not a planar structure but a three-dimensional interior. An oil-in-water emulsion in which oil droplets are coated with a self-micellar aqueous dispersion of fumed silica particles that is stable and uniform by promoting the exchange and / or orientation of silica particles while forming a surrounding structure. Pickering emulsion) can be produced.
More specifically, in an oil-in-water pickering emulsion, the hydrophobic / hydrophilic ratio of the fumed silica particles present at the interface between the aqueous phase and the oil phase is important for the stability of the emulsion, while In fumed silica having extremely high agglomeration, for example, in a secondary agglomerate formed by aggregating primary agglomerates, a network between the primary agglomerates or a secondary agglomerate. By forming a network between them, and in particular, by forming a network-like surrounding structure containing oil inside, the optimum contact angle (embedding degree) of the fumed silica particles at the interface between the aqueous phase and the oil phase is optimized. The conversion is promoted.
When forming a dispersion of fumed silica and water, due to its high cohesiveness, fumed silica begins to form a network structure simply by adding the fumed silica to water without shearing. By applying shear, the formed network structure is disassembled, and while forming a new network structure, the arrangement or orientation between the primary aggregates is promoted, and the hydrophobic rich aggregates and self-micellar coagulation are promoted. Aggregates and hydrophilic-rich aggregates each form a network structure, as well as a network-like structure between hydrophobic-rich aggregates, automicellar aggregates and hydrophilic-rich aggregates, especially automicellar aggregates. , Form a network-like surrounding structure containing oil inside.
According to the present invention, since the specifications of the composite particles in the oil-in-water emulsion can be adjusted, stable, uniform and highly reliable composite particles can be isolated.

In the oil-in-water pickering emulsion using solid particles, the balance between the hydrophilicity and hydrophobicity of the solid particles existing at the interface between the aqueous phase and the oil phase is the balance of the emulsion, as opposed to the oil-in-water emulsion using a surfactant. Although known to be an important factor for stability, we have found that, especially in the case of silica particles, the fumed silica particles are due to the high agglomeration of the fumed silica particles. When the group forms a network, it forms a surrounding structure that forms a space inside a three-dimensional structure instead of a planar structure, and by adding oil based on the aqueous dispersion in which silica particles are dispersed in water. , Discovered that forming an oil-in-water pickering emulsion is important for emulsion stability, and based on this fact, the mechanism of formation of the composite particle structure of silica particles and oil in the pickering emulsion is silica. Silica is a parameter for evaluating not only the stability of oil-in-water pickering emulsion but also the stability of an aqueous dispersion in which silica particles are dispersed in water, based on the uniqueness due to the agglomeration of particles. By paying attention to the so-called total molar number ratio and the variation in the total molar ratio between the surface hydrophilic group and the surface hydrophobic group of the particles, it is possible to relax the restrictions on the selection of the silica particles and the oil content as starting materials, and also for the application. It has been found that the stability and characteristics of the aqueous dispersion can be compatible with each other, and the composite particle structure in the emulsion can be adjusted according to the application.

Silica is preferably used as the inorganic particles used as a raw material for the aqueous dispersion of the inorganic particles of the present invention. There are various types of silica such as fumed silica, wet silica, and colloidal silica. In all types of silica particles, hydrophilic silanol is present on the surface and the silanol group is alkylated at an arbitrary ratio. Since the hydrophobic treatment with a group or the like can be performed, it is easy to set the molar ratio of the hydrophilic group to the hydrophobic group on the surface. In addition, silica has a cohesive structure, has a high affinity with various oils, is easily transferred to pickering emulsions, and has a wide range of uses from the viewpoints of availability and economy. preferable.
The silica particles do not necessarily occupy 100% of the inorganic particles, and may be partially contained. Silica particles form a network with inorganic particles other than silica particles, and while silica particles play a leading role in making the aqueous dispersion exist stably and uniformly, other inorganic particles play a supporting role. Because it can be done.

The most preferable silica as a raw material for the aqueous dispersion is fumed silica.
The fumed silica particles have a multi-order aggregated structure. Therefore, the balance between the hydrophilic group and the hydrophobic group on the surface can be controlled or the aggregation unit can be recombined according to the aggregation level. Therefore, in carrying out the present invention, the stability and uniformity of the aqueous dispersion can be controlled most effectively.
Further, since the fumed silica particles have a porous structure, the surface area becomes large and the functions of association and adsorption become larger, so that an aqueous dispersion can be produced more stably and uniformly. In addition, since the functions of associating with various oils and adsorbing are enhanced, it is also advantageous when migrating to a pickering emulsion.

The primary particles, which are the smallest units of fumed silica particles, usually have a size of about 5 to 30 nanometers, and the primary particles aggregate to form primary aggregates, that is, secondary particles. .. The size of the primary aggregate is usually about 100 to 400 nanometers. Since the primary particles are fused by chemical bonds, it is usually difficult to separate the primary aggregates. Further, the primary aggregates form an aggregate structure, which is referred to as a secondary aggregate, that is, a tertiary particle. The size of the secondary aggregate is about 10 μm. The agglomeration morphology between the primary agglomerates in the secondary agglomerates is usually due to hydrogen bonds or other associative cohesive forces rather than chemical bonds. Therefore, it is also possible to separate some or all of the secondary aggregates to the level of the primary aggregates by applying some external force. For example, a certain amount of shearing force is applied in water. The separated secondary aggregates aggregate again as secondary aggregates when an external force is applied.

In the description of the present invention, the primary and secondary aggregates may be appropriately referred to as silica particle groups at the primary and secondary aggregation levels.
Fumeed silica particles, in powder form, are often the highest level of agglomeration of secondary agglomerates. However, in the context of aqueous dispersions, secondary aggregates can further aggregate. The force for separating the agglomerates can be weaker than the force for separating the secondary agglomerates.
However, the above-mentioned aggregation levels of primary aggregates and secondary aggregates are not always clearly formed, and for example, aggregation levels such as the intermediate stage between primary aggregates and secondary aggregates are also available. It may be distributed continuously to some extent and mixed. Including the width of such distribution, it will be referred to as a primary aggregate and a secondary aggregate.
Fused silica particles are also known to have a network structure, especially at the secondary aggregation level, which may be easy to use as inorganic particles for pickering emulsions.
More specifically, FIG. 1 (only a schematic diagram, originally a network-like surrounding structure of fumed silica particles covers the entire outer peripheral surface of the oil droplets, but is shown in a cross-sectional view for ease of viewing. As shown in), the fumed silica particles form a network due to the high agglomeration of the fumed silica particles. The network is not a planar structure, but forms a surrounding structure that forms a space inside a three-dimensional shape, and as will be described later, it is interfacially active in forming an aqueous dispersion of fumed silica particles and water. Although the fumed silica particles that function as agents exist on the surface of the oil droplets, which is the interface between the aqueous phase and the oil phase (oil droplets), they form a surrounding structure that forms a space inside the three-dimensional shape. However, when oil is added to such an aqueous dispersion afterwards, it becomes a form that covers the oil droplets.
Therefore, as will be described later, by identifying aggregates of fumed silica particles covering the outer peripheral surface of a single oil droplet based on a single oil droplet, self-micellar aggregates and hydrophilic rich aggregates are identified. And it is considered possible to distinguish between hydrophobic rich aggregates.

Hereinafter, the state of the aqueous dispersion of inorganic particles according to the present invention in water, the method for producing the aqueous dispersion, and the use thereof will be described when fumed silica is used as a raw material. In that description, the use of the term primary agglomeration level and secondary agglomeration level means that the description is not 100% about that level alone, but is primarily about that agglomeration level.
Even in the case of an aqueous dispersion of inorganic particles other than fumed silica, the basic parts are common.

FIG. 2 shows what kind of aggregates can be formed when the fumed silica particles are dispersed in water. In the present specification, the terms hydrophilic rich aggregate, hydrophobic rich aggregate, and self-micellar aggregate are used for convenience. Self-micellar aggregates are a novel concept found in the present invention. Further, in the present invention, the relationship between these three types of aggregates has been found and will be described.
When the molar ratio of hydrophilic groups / hydrophobic groups on the surface of the fumed silica particles is rich in hydrophilic groups, the surface of the silica particles is compatible with water, so that the silica particles are easily dissolved in water and the secondary aggregate 14 is the same. In many cases, they do not aggregate and are stably dissolved in water by themselves. The viscosity of the aqueous dispersion is low and the thixotropic property is low. Such aggregates will be referred to as hydrophilic rich aggregates.
When the molar ratio of hydrophilic groups / hydrophobic groups on the surface of the fumed silica particles is rich in hydrophobic groups, the surface of the silica particles and water are difficult to be compatible with each other. Since the silica particles tend to be arranged with each other, the silica particles tend to aggregate. A large number of secondary aggregates 14 gather together in water to form an aggregate. Therefore, the viscosity of the aqueous dispersion becomes high, and the thixotropic property becomes high. In this state, the stability of the aqueous dispersion is not good. Sedimentation of silica particles and the like are likely to occur over time. Such aggregates will be referred to as hydrophobic rich aggregates. This state has already been used as a thickening agent and a thixotropy-imparting agent as hydrophobic fumed silica. However, there is a restriction that the user must disperse the silica particles in water and immediately put them into the target material.
When the molar ratio of hydrophilic groups / hydrophobic groups on the surface of the fumed silica particles is in the region between the hydrophilic rich aggregates and the hydrophobic rich aggregates, the secondary aggregate 14 has a relatively high degree of hydrophilicity. It is possible to form an aggregate in which the dense portion of the aggregate 10 is in contact with the aqueous phase and the dense portion of the primary aggregate 12 having a relatively high hydrophobicity is in contact with other secondary particles. Since it has an aggregated form similar to that of a normal surfactant self-micelle, it is referred to as an automicellar aggregate. In this state, the number of aggregates of the secondary aggregates 14 is limited to a small number, and the size of the aggregates is naturally homogeneous, so that a stable and uniform aqueous dispersion is obtained. Since the concentration of the hydrophilic group is high on the outside of the self-micellar aggregate, that is, the portion in contact with the aqueous phase, it is possible to obtain sufficiently high stability similar to that of the hydrophilic rich aggregate. It is much more stable than hydrophobic rich aggregates. Since there is a space 16 inside the self-micellar aggregate and the environment is lipophilic, it is easy to take in oil from the outside. The viscosity and thixotropic properties of self-micellar aggregates are intermediate properties between hydrophilic-rich aggregates and hydrophobic-rich aggregates. Surfactant self-micelles are formed when the surfactant is in excess due to the relationship with the oil to be emulsified, but in fumed silica particles, it depends on the presence of oil and the concentration. It is not easily affected and can be formed.

In the case of a surfactant, at a low concentration, it sufficiently interacts with water molecules and dissolves in the state of one molecule or one ion of the surfactant (monodisperse state), but at a certain concentration or higher, it is simply. The concentration in the dispersed state becomes the saturated concentration, and the subsequent surfactants associate to form supermolecules or self-assembled bodies, which are so-called automicelles. Automicelles are usually an association structure with the hydrophilic part on the outside and the hydrophobic part on the inside.
Similarly, in the water-dispersed state of silica at the secondary aggregation level, the present inventors have a self-micellar aggregate having an association structure in which such a hydrophilic portion is on the outside and the hydrophobic portion is on the inside if the saturation concentration is exceeded. It is noted that is formed. However, the saturation concentration is much lower than that of the surfactant.

The definitions of these three types of aggregates relative to each other are as follows.
Hydrophobic rich agglomerates, as agglomerates of fumed silica particles, exhibit hydrophobicity to the extent that they exhibit thixotropic properties as compared with self-micellar agglomerates and hydrophilic rich agglomerates, and have a high aggregation level of fumed silica. Agglomerates of a group of particles, hydrophilic rich agglomerates, as agglomerates of fumed silica particles, exhibit hydrophobicity enough to dissolve in water as compared with self-micellar agglomerates and hydrophobic rich agglomerates, and the aggregation level is high. A mass of low fumed silica particles, a self-micellar agglomerate, is an agglomerate of fumed silica particles that is more hydrophobic on the inside and hydrophilic on the outside as compared to hydrophobic rich agglomerates and hydrophilic rich agglomerates. It is a mass of fumed silica particles that is expressed and the aggregation level is located between the hydrophobic rich aggregate and the hydrophilic rich aggregate. It has a space inside and is pro-oil-like, and has a structure that easily takes in oil from the outside. ..
Inorganic particles other than fumed silica particles may also have such three types of aggregated morphology.

In order to produce an aqueous dispersion of fumed silica particles, it is difficult for the raw material silica particles to spontaneously dissolve or disperse in water regardless of the type of agglomerate formed, so some shearing force is applied. It is necessary to use a device that gives. It can be produced by using an ordinary mixer, for example, a homogenizer, a colloid mill, a homomixer, a high-speed stator rotor stirrer, or the like.

The blending amount of the fumed silica particles in the aqueous dispersion is preferably in the range of 0.1 to 30.0% by mass, more preferably in the range of 0.2 to 10% by mass, based on the total amount of the aqueous dispersion composition. preferable. If the blending amount is less than 0.1% by mass, aggregation may not proceed, and if the blending amount exceeds 30.0% by mass, the viscosity increases, which exceeds the appropriate range of the stirring device.

The cohesive force between the primary aggregates of the fumed silica particles is released when a specific shearing force is applied, and reaggregates when the shearing is stopped. Therefore, in the production of aqueous dispersions, if specific shear is applied, due to the high cohesiveness of the fumed silica particles, when the fumed silica particles form a network, they are not a planar structure but a three-dimensional structure. It is also possible to exchange primary aggregates between separate secondary aggregates while forming a surrounding structure that forms a space inside. Thereby, the ratio of the hydrophilic-rich primary aggregate and the hydrophobic-rich primary aggregate in one secondary aggregate can be changed. The exchange of primary aggregates among such secondary aggregates will be referred to as rearrangement.
In order to cause rearrangement, it is preferable to apply a shear rate of 7500s ^-1 or higher. If the shear rate is less than 7500s ^-1 , sufficient rearrangement will not occur. There is no upper limit of the shear rate for raising the rearrangement, but if it exceeds 100,000s ^-1 , problems on the device are likely to occur, and the water is evaporated or the oil content is released due to the heating of the aqueous dispersion. In some cases, problems such as decomposition may occur, which is not preferable.
Sufficient rearrangement promotes the exchange of primary aggregates between secondary aggregates, and thus the hydrophilicity of the fumed silica particles throughout the system of aqueous dispersions in the secondary aggregates. The ratio of the rich primary aggregate to the hydrophobic rich primary aggregate becomes more uniform.
Also, when a sufficient shear rate is applied to the agglomerates of silica particles for rearrangement to occur, the planes of the fumed silica particles form a network due to the high agglomeration of the fumed silica particles. While forming a surrounding structure that forms a space inside a three-dimensional structure instead of a shaped structure, movement of the primary agglomerates may occur in the same secondary agglomerates, and the arrangement may change. Then, when self-micellar aggregates are formed, as shown in FIG. 2, the hydrophobic primary aggregates may be oriented toward the aggregation direction of the two particles.

As shown in the above description and graphically in FIG. 2, the types of aggregates most likely to form differ depending on the degree of hydrophilicity / hydrophobicity of the fumed silica particles.
More specifically, the total number of moles of surface hydrophilic groups in each of the fumed silica particle groups over the fumed silica particle group / the number of moles of surface hydrophobic groups in each of the fumed silica particle groups. If the total number of moles ratio, which is the total number of moles over the group, is not more than a predetermined lower limit, hydrophobic rich aggregates are mainly produced. When the total molar ratio is equal to or higher than a predetermined upper limit, hydrophilic rich aggregates are mainly produced. When the total molar ratio is not less than a predetermined lower limit and not more than the upper limit, self-micellar aggregates are mainly produced.
In the case of fumed silica, the lower limit of the total molar ratio is approximately 20/80. The upper limit is approximately 80/20.

In the present invention, it has been unexpectedly discovered that the state of fumed silica as a starting material is not restricted as long as a certain amount of shearing force is applied in order to cause rearrangement of the particles of fumed silica. That is, at the raw material stage, the total number of moles of the surface hydrophilic groups in each of the fumed silica particles groups is the total number of moles over the fumed silica particles group / the number of moles of the surface hydrophobic groups in each of the fumed silica particles groups is the number of moles of the fumed silica particles. The type of silica as a raw material does not matter as long as the total number of moles ratio, which is the total number of moles over the group, is set to 20/80 or more and / or 80/20 or less. Hydrophilic silica particles having residual silanol groups on the surface or hydrophobic silica particles obtained by hydrophobizing the silanol groups on the surface may be used, and these may be arbitrarily mixed and used. Further, fumed silica which has been hydrophobized at an arbitrary ratio may be used. Commercially available fumed silica particles can be used. Alternatively, the hydrophilic silica particles can be hydrophobized by a known method of treating with a halogenated organosilicon such as methyltrichlorosilane, alkoxysilanes such as dimethyldialkoxysilane, silazane, or low molecular weight methylpolysiloxane. can.
The above silica particles preferably have a specific surface area of 2 to 350 m ² / g in a dry state, and are particularly preferably 50 to 300 m ² / g.

As the raw material, the above-mentioned types of fumed silica particles can be used, but at the raw material stage, the total number of moles of the surface hydrophilic groups in each of the fumed silica particle groups is the total number of moles over the fumed silica particle group / fumed silica particle group. It is necessary to set the total number of moles ratio, which is the total number of moles of the number of moles of the surface hydrophobic group in each of the fumed silica particle groups, to 20/80 or more and / or 80/20 or less.
In this case, when forming an aqueous dispersion of water and the fumed silica particle group, a certain level of shearing force is applied by filling the water with the fumed silica particle group due to the high aggregation property of the fumed silica particles. Previously, a network structure was formed by fumed silica particles, but this network structure is mainly a network structure between secondary aggregates, and if some external force such as shearing is applied, the secondary aggregates will be primary aggregated. It is possible to separate part or all of the particles by the time they are aggregated, and by applying a certain amount of shearing force, the network structure is disassembled, and as described above, again at the primary aggregate level, three-dimensional. Exchange and / or 2 at the primary aggregation level between the fumed silica particle groups at the secondary aggregation level based on the aggregation of the fumed silica particles while forming a network-like surrounding structure that forms a space inside. By promoting the orientation of the fumed silica particles at the secondary aggregation level at the primary aggregation level, self-micellar aggregates having a high density of hydrophilic portions on the outside and hydrophobic portions on the inside become the main constituents, and the self is the main constituent. It becomes possible to promote homogenization between micellar aggregates.

The aqueous dispersion of inorganic particles obtained by the present invention is stable and uniform, which has not existed in the past, and is also provided with functions such as thickening and imparting thixotropy, so that many new applications can be opened up. In addition, using commercially available silica, the molar ratio of hydrophilic groups and hydrophobic groups can be adjusted at the raw material stage, and the product can be manufactured with a normal device, which produces a great advantage in terms of cost and positive.

According to the present invention, by setting the total molar ratio of fumed silica particles, it is possible to change the abundance ratio of hydrophobic rich aggregates, hydrophilic rich aggregates, or self-micellar aggregates. This makes it possible to develop new applications.
Self-micellar aggregates have thickening and thixotropic effects, though not as much as hydrophobic rich aggregates. Moreover, it is excellent in stability and uniformity.
Therefore, if the total molar ratio is set to 20/80 or more, self-micellar aggregates and hydrophobic rich aggregates are mixed. In such a case, the stability is improved as compared with the conventional thickener and thixotropy-imparting agent using hydrophobic fumed silica. That is, new applications that emphasize both stability and viscosity / thixotropic properties become possible. For example, when added to paints and polymer materials to impart viscosity and thixotropic properties, it is not unstable as in the case of conventional silica particles that settle immediately, so it can be commercialized as a stable aqueous dispersion. It will be possible. The storage stability for the user is increased, and the user does not need to prepare the aqueous dispersion, so that the ease of handling is improved.

If the total molar ratio is set to 80/20 or less, self-micellar aggregates and hydrophilic rich aggregates are mixed. In such a case, although the conventional hydrophilic fumed silica has good stability, the thickening and thixotropic properties are increased to some extent as compared with the case where the thickening and thixotropic properties are hardly obtained. That is, new applications that emphasize both stability and low viscosity become possible. For example, new applications can be opened up in cases where a small degree of viscosity increase and thixotropy are required, such as creams and milky cosmetics, and where good stability is required. In addition, the storage stability for the user is good, and the user does not need to prepare the aqueous dispersion, so that the ease of handling is improved.

When the total molar ratio is set to 20/80 or more and 80/20 or less, the self-micellar aggregate is present in the center. In this case, it is stable and has a certain degree of viscosity and thixotropic property. Further, since there are no hydrophobic rich aggregates or hydrophilic rich aggregates, the state is uniform.
Therefore, it is possible to provide a stable and uniform function-imparting agent centered on thickening and thixotropic property, and it is possible to develop a very wide range of applications. It is possible to reduce yesterday's variability and batch-to-batch variability within the same batch. There are many conceivable uses for which such features can be utilized, such as cosmetics, functional paints, functional coating agents, adhesives, and building sealants. Moreover, the degree of thickening and thixotropic property imparting desired for each application can be adjusted by appropriately adjusting the total molar ratio. In addition, the storage stability for the user is good, and the user does not need to prepare the aqueous dispersion, so that the ease of handling is improved.

The pickering emulsion according to the present invention contains a composite particle group in the form of oil contained in the self-micellar aggregate formed by the fumed silica particle group of the secondary aggregate, and each of the composite particle groups is self-micellar. An oil-in-water emulsion in which agglomerates cover the surface of oil droplets. The stability of self-micellar aggregates in aqueous dispersions basically also applies to pickering emulsions.
The oil droplets are coated with self-micellar aggregates to produce a stable, uniform and reproducible pickering emulsion.

It is said that the size of the secondary aggregate of fumed silica is about 10 μm in the normal existence form. However, in the oil-in-water emulsion according to the present invention, a mass of spherical silica particles is coated, and one mass is often in the size of about 0.1 μm to several μm. Therefore, even if it is called a secondary aggregate, it may contain a primary aggregate in a small part and an aggregate in an intermediate stage from the primary to the secondary. Alternatively, it is possible that the secondary aggregates are formed more densely than they generally exist.

The oil content contained in the oil-in-water emulsified composition of the present invention is not limited, and any kind of oily component can be used. For example, silicone, mineral oil, synthetic oil, vegetable oil, animal oil, etc. can be used.
Silicone is a preferable oil because it gives excellent properties in a wide range of applications such as industrial use and cosmetics. The type is not limited. For example, chain polysiloxane (eg, dimethylpolysiloxane, methylphenylpolysiloxane, diphenylpolysiloxane, etc.), cyclic polysiloxane (eg, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, etc.), Silicone resin, silicone rubber, various modified polysiloxanes (amino-modified polysiloxane, polyether-modified polysiloxane, alkyl-modified polysiloxane, fluorine-modified polysiloxane, etc.) forming a three-dimensional network structure, alkenyl-modified polysiloxane, hydrogen Examples thereof include polysiloxane and acrylic silicones.

The viscosity of the oil is also not limited. Further, as long as it has fluidity, it may contain a solid component. Further, a rubber having fluidity or a rubber-containing material, or a curable rubber composition that cures after forming an emulsion to become rubber may be used.

When the oil contained in the oil-in-water emulsified composition is a fluorine-containing organopolysiloxane, the average composition formula is represented by the general formula (1).
R ¹ _a R ² _b SiO _{(4-ab) / 2} (1)
[In formula (1), R ¹ may be the same or different in the molecule, and is a substituted or unsubstituted saturated or unsaturated monovalent hydrocarbon group having 1 to 25 carbon atoms, substituted or unsubstituted. It is an aromatic group having 6 to 30 carbon atoms, a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms or a hydrogen atom, and R ² may be the same or different in the molecule and has 1 to 25 carbon atoms. Saturated or unsaturated monovalent hydrocarbon group, or an aromatic group having 6 to 30 carbon atoms, in which a hydrogen atom on at least one carbon is substituted with a fluorine atom, and b is not 0. Positive number, a + b is greater than or equal to 0.3 and less than 2.5]
a and b are numerical values related to the order of the siloxane bond, and if a + b is 2.0, the component (A) indicates a linear siloxane. In the present invention, since a + b is 0.3 or more and less than 2.5, the component (A) may be in any form of oil, rubber, resin, curable composition and the like.

Specifically, the above-mentioned organic group R ¹ includes a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, a neopentyl group, a hexyl group, a 2-ethylhexyl group and a heptyl. Alkyl group such as group, octyl group, nonyl group, decyl group, dodecyl group; cycloalkyl group such as cyclopentyl group, cyclohexyl group, cycloheptyl group; aryl such as phenyl group, trill group, xylyl group, biphenyl group and naphthyl group Group; Aralkyl group such as benzyl group, phenylethyl group, phenylpropyl group, methylbenzyl group; -CH ₂ -CH ₂ -CH ₂ -N ₂ , -CH ₂ -CH ₂ -CH ₂ -NH (CH ₃ ), -CH ₂ -CH ₂ -CH ₂ -N (CH ₃ ) ₂ , -CH ₂ -CH ₂ -NH-CH ₂ -CH ₂ -NH ₂ , -CH ₂ -CH ₂ -CH ₂ -NH (CH ₃ ) , -CH ₂ -CH ₂ -CH ₂ -NH-CH ₂ -CH ₂ -NH ₂ , -CH ₂ -CH ₂ -CH ₂ -NH-CH ₂ -CH ₂ -N (CH ₃ ) ₂ , -CH ₂ -CH ₂ -CH ₂ -NH-CH ₂ -CH ₂ -NH (CH ₂ CH ₃ ), -CH ₂ -CH ₂ -CH ₂ -NH-CH ₂ -CH ₂ -N (CH ₂ CH ₃ ) ₂ , -CH ₂ -CH ₂ -CH ₂ -NH _- CH ₂ - _Ch Chloromethyl group, 2-bromoethyl group, 3,3,3-trifluoropropyl group, 3-chloropropyl group, chlorophenyl group, dibromophenyl group, tetrachlorophenyl group, difluorophenyl group, substituted with atomic, cyano group, etc. Examples thereof include a substituted hydrocarbon group such as a β-cyanoethyl group, a γ-cyanopropyl group and a β-cyanopropyl group.
Particularly preferable organic groups are a methyl group and a phenyl group.
Further, a substituent that causes a curing reaction, for example, an unsaturated hydrocarbon group such as a vinyl group or an allyl group, hydrogen bonded to a silicon atom, or the like may be contained.

The above-mentioned organic group R ² is a saturated or unsaturated monovalent hydrocarbon group having 1 to 25 carbon atoms or an aromatic group having 6 to 30 carbon atoms, and specifically, the saturated or unsaturated group exemplified as R ¹ . A saturated monovalent hydrocarbon group or an aromatic group, which is an organic group in which a hydrogen atom on at least one carbon is substituted with a fluorine atom.

In the fluorine-containing organopolysiloxane, the number of moles a per mole of the silicon atom of the organic group R ¹ and the number of moles b per mole of the silicon atom of the organic group R ² are positive numbers where b is not 0 and a + b is 0. It is not limited as long as it is 3 or more and less than 2.5.
It is preferable that a + b is 0.8 or more and less than 2.2. If it is less than 0.8, the proportion of tetrafunctional resin increases, and it is difficult to produce an emulsion because it is solid. If it is 2.2 or more, the silane component increases, the volatility becomes high, and it is difficult to apply it to various applications. be.
The ratio of the organic group R ¹ and the organic group R ² , that is, a / b is not limited, but is preferably 5/95 or more and less than 95/5. If it is less than 5/95, the characteristics as a normal organopolysiloxane, for example, flexibility, are not sufficiently exhibited, and if it is 95/5 or more, the content of organic groups containing fluorine is low, so that it is derived from fluorine. This is because the characteristics cannot be fully brought out.

As long as the above conditions are satisfied, the chemical structure, molecular weight, or properties of the fluorine-containing organopolysiloxane are not limited. Further, the form may be any of liquid, solid, flake-like, powder and the like.
Further, the fluorine-containing organopolysiloxane may be either a single component or a mixture of two or more kinds of components.

It is preferable that neither the organic group R ¹ nor the organic group R ² contains a hydrophilic substituent such as a hydroxyl group, a carboxyl group, an amino group or an alkoxy group. This is because the water repellency and water resistance inherent in the fluorine-containing organopolysiloxane are sacrificed in the intended use.

In the individual composite particles present in the oil-in-water emulsion according to the present invention, self-micellar aggregates of fumed silica particles cover the oil droplets. At that time, it may be covered with a layer of each secondary aggregate, or it may form a plurality of layers of the secondary aggregate. Alternatively, there may be a portion that is not partially covered with the fumed silica particles.
The secondary aggregate in contact with the oil droplet is partially embedded in the oil droplet. The degree of embedding depends on the degree of polarity of the oil and the molar ratio of hydrophilic and hydrophobic groups on the surface of the fumed silica secondary aggregate. When the polarities of the oil droplets and the secondary aggregates are close, for example, when the silicone is an oil droplet and the polarity of the surface of the secondary particles is close to that of silicone, the affinity is large and the degree of embedding is large. .. On the contrary, when the difference in polarity is large, the degree of embedding is small.
In order for the pickering emulsion to exist stably, it is said that it is important to take the contact angle determined by the three factors of inorganic particles, oil droplets and water as the optimum value. In the oil-in-water emulsion of the present invention, the degree to which the secondary aggregates of the fumed silica particles are embedded in the oil droplets is mainly determined by the above mechanism, but in the process of completing the emulsion, the fumes are subjected to an appropriate shearing force. Due to the high agglomeration of the dosilica particles, when the fumed silica particles form a network, they form a surrounding structure that forms a space inside the three-dimensional structure instead of a planar structure, and the secondary agglomerates. The primary agglomerates of the above may move and the highly hydrophobic primary particles may be oriented toward the oil droplets, resulting in a polar gradient within the secondary particles. In order for the emulsion to be present most stably, it is possible that the optimum contact angle is obtained by determining the degree of embedding by adjusting the degree of inclination described above by itself.
In addition, the secondary aggregate can move under an appropriate shearing force even after the emulsion is formed. It is also possible to move the surface of the oil droplets to make them evenly spaced, and to make the state of lamination uniform. Furthermore, some can be moved back and forth between other composite particles.

The coating of oil droplets with secondary aggregates of fumed silica particles includes a partial coating in addition to a full coating. As an index showing the degree of coating, the thickness of the silica layer and the result of morphological observation can be considered, but by taking up the coating amount this time, the characteristics can be controlled as a more practical degree of coating. The characteristics refer to the characteristics as an emulsion (stability, etc.) and, when isolated and used as composite particles, the non-blocking properties of the isolated composite particles.
The amount of the coating layer of the silica particles on the surface can be parameterized as the weight of the fumed silica particles per unit area of the surface of the oil droplet.
In the present invention, the amount of the silica coating layer can be controlled by the amount of treated silica particles with respect to the surface area calculated from the particle size of the composite particles. This amount is preferably in the range of 2.0 × 10 ^-9 to 3.2 × 10 ^-6 kg / m ² . If it is less than 2.0 × 10 ^-9 kg / m ² , blocking of the composite particles in water or after isolation will occur, and if it exceeds 3.2 × 10 ^-6 kg / m ² , the friction of the composite particles will increase. For these reasons, unfavorable phenomena such as squeaky feeling in cosmetics, contamination with excess silica in the emulsion or after isolation of particles, etc. occur in a specific application.

The particle size of the individual composite particles present in the oil-in-water emulsion according to the present invention is affected by the mass ratio of the fumed silica particles to the total amount of oil. The higher the ratio, the smaller the particle size. However, within the above-mentioned preferable amount of the silica coating layer, the particle size is about 10 μm regardless of the type of oil. Although it is larger than the particle size of the particles of the emulsion emulsified by a normal organic surfactant, it is stable and uniform at this particle size, and when applied to various applications, the particles of the pickering emulsion are approximately 100 μm or less. Any diameter is suitable. If the particle size exceeds 100 μm, the stability of the emulsion will decrease, and when composite particles are isolated and used, for example, in cosmetic applications, the size of the powder will be a region that can be felt by touch, so from the viewpoint of usability. Not preferable.
The variation in the particle size of the composite particle group present in the oil-in-water emulsion according to the present invention is small. This is because the surface of the oil droplets is covered with self-micellar aggregates of fumed silica particles. Since the self-micellar aggregate of the aqueous dispersion is uniform, the action on the oil droplets is uniform, and the variation in particle size is small.

Further, it may have a step of blending the fumed silica particle group at the secondary aggregation level and the organic surfactant at a predetermined blending ratio so as to adjust the morphology of the network-like surrounding structure. The step of blending the fumed silica particles and the organic surfactant in the above step is to determine a predetermined blending ratio so as to adjust the adhesion of the self-micellar aggregate to the oil droplets surrounded by the self-micellar aggregate. It may be included.
More specifically, the secondary aggregation level fumed silica particles and the organic surfactant are both present on the outer surface of the oil droplets, which is the interface between the aqueous phase and the oil phase, the aqueous phase, the oil phase and In the three-way relationship between the fumed silica particles at the secondary aggregation level and the organic surfactant, the contact angle (embedding degree) of the fumed silica particles at the secondary aggregation level and the organic surfactant with respect to the oil droplets is determined. That is why, compared to the case where only the fumed silica particles at the secondary aggregation level are present at the interface without containing the organic surfactant, the fumed silica particles and the organic surfactant at the secondary aggregation level are present. If ), Which requires trial and error, but the specifications of the composite particles consisting of self-micellar aggregates and oils, such as the size, shape, and secondary aggregation of the composite particles. The stickiness of the level of fumed silica particles to oil droplets can be adjusted.
In this case, the mass ratio of the fumed silica particles to the total amount of oil may be further combined with the blending ratio of the fumed silica particles at the secondary aggregation level and the organic surfactant.

In order to produce an oil-in-water emulsion according to the present invention, it can be produced by using an apparatus similar to the apparatus used for producing an aqueous dispersion of fumed silica particles.
In order to coat the surface of the oil droplets with the self-micellar aggregates of the fumed silica particles, a method of first forming the self-micellar aggregates of the fumed silica particles and then adding the oil is adopted. There is a need. This is because when the oil is added first, self-micellar aggregates of the fumed silica particles are not formed, so that the oil-in-water emulsion which is the desired pickling emulsion cannot be obtained.
Therefore, as a production method, as a first step, the total number of moles of the surface hydrophilic groups in each of the fumed silica particle groups over the fumed silica particle group / the molar of the surface hydrophobic group in each of the fumed silica particle groups. A group of fumed silica particles having a secondary aggregation level is prepared so that the total number of moles ratio, which is the total number of moles over the number of fumed silica particle groups, is 20/80 or more and 80/20 or less. In order to keep the total molar ratio within a predetermined range, the molar ratio is adjusted with the raw material fumed silica in the same manner as in the method for producing self-micellar aggregates of the aqueous dispersion.
Next, as a second step, the prepared group of fumed silica particles having a secondary aggregation level is added to water and sheared at a predetermined shear rate to obtain the fumed due to the high cohesiveness of the fumed silica particles. When the silica particle group forms a network, it forms a surrounding structure that forms a space inside a three-dimensional structure instead of a planar structure, and at the primary aggregation level between the fumed silica particle groups at the secondary aggregation level. By promoting exchange and / or orientation at the primary aggregation level in the fused silica particles at the secondary aggregation level, the average value of the total molar number ratio and in each of the secondary particles constituting the fumed silica particle group. An aqueous dispersion containing self-micellar aggregates of fumed silica particles at the secondary aggregation level so that the difference from the molar ratio, which is the number of moles of surface hydrophilic groups / the number of moles of surface hydrophobic groups, is less than a predetermined value. Generate. In order to cause rearrangement, it is preferable to apply a shear rate of 7500s ^-1 or higher.
Next, as a third step, an oil component is added to the produced aqueous dispersion to form an emulsion. At this time, in the stirring device, an appropriate shearing rate is applied, and it takes time to appropriately shear the self-micellar aggregates in order to uniformly cover the surface of the oil droplets and uniformly form the structure as composite particles. The shear rate does not need to be 7500 s ^-1 or more at which rearrangement occurs, and usually several thousand s ^-1 is sufficient.

The total number of moles of surface hydrophilic groups in each of the fumed silica particle groups over the fumed silica particle group / the total number of moles of surface hydrophobic groups in each of the fumed silica particle groups over the fumed silica particle group. It is important to centrally produce self-micellar aggregates by setting a certain total number of mole ratio within a predetermined range in order to produce a stable and uniform pickering emulsion. The state of the self-micellar aggregates (for example, the degree of embedding of the secondary aggregates in the oil droplets at the interface) in the individual composite particles in which the surface of the oil droplets is coated with the self-micellar aggregates does not vary as much as possible. Is preferable. If the variation is small, the cooperation between the self-micellar aggregates becomes stronger, and therefore the composite particles tend to become more stable. As a result, the entire composite particle group becomes stable, and the variation in the state between the individual composite particles becomes smaller.

In order to reduce the variation among the secondary aggregates, the second step in the above-mentioned production method is performed. The small variation in the degree of hydrophobicity (hydrophilicity) among the secondary aggregates also reduces the variation in the degree of embedding of the secondary aggregates in contact with the oil droplets in each self-micellar aggregate. The variation in the degree of hydrophobicity (hydrophilicity) for each secondary aggregate is stable if it is within 60% of the average value of the variation in the degree of hydrophobicity (hydrophilicity) of all secondary aggregates. An oil-in-water emulsion is formed.
In order to reduce the variation between secondary aggregates, particles in which hydrophilic groups are hydrophobized at a specific hydrophobicization rate are used as raw material fumed silica particles without shearing to cause rearrangement. It is also achieved by using it. However, the method requires a large manufacturing cost. Even without using such special silica particles, commercially available and inexpensive hydrophilic fumed silica particles and hydrophobic fumed silica particles are used as raw materials, and the mass ratio is adjusted so as to have a predetermined total molar ratio. This is because it can be manufactured by a simple method just by doing so.

Even if the variation in the degree of hydrophobicity (hydrophilicity) of the secondary aggregate is not significantly reduced, the variation in the state of the composite particle is caused by promoting the orientation of the fumed silica particles at the secondary aggregation level at the primary aggregation level. It can also be reduced. As the orientation progresses, the concentration of hydrophobic groups increases in the vicinity of the portion of the secondary aggregate in contact with the oil droplet interface, and conversely, the concentration of hydrophilic groups increases in the vicinity of the portion in contact with the aqueous phase, and embedding in the oil droplets. This is because both the affinity with the aqueous phase and the affinity with the aqueous phase can be efficiently performed.
When the variation in the degree of hydrophobicity (hydrophilicity) of the secondary agglomerates is reduced and the orientation of the fumed silica particles at the secondary agglomeration level is advanced at the primary agglomeration level, a synergistic effect is exhibited. More stable and uniform composite particles can be produced.

In terms of variation among composite particles, it is also important to set the mass ratio of fumed silica particles and oil. As described above, the coating thickness of the silica particles on the surface of the oil droplet should not vary among the composite particles as much as possible. For that purpose, it is preferable to set the mass of the silica particles within the range of the above-mentioned stable coating amount with respect to the mass of the oil content.
When silica is also used as functional particles in the oil-in-water emulsion or isolated composite particles of the present invention, the mass ratio of oil to silica particles is also important.

The oil-in-water emulsion (pickering emulsion) in which the fumed silica particles obtained by the present invention coat the oil droplets secures the main stability and uniformity at the stage of forming the aqueous dispersion, and is auxiliary to the main stability and uniformity. Stabilization is applied, which greatly enhances stability and uniformity. In addition, it has good reproducibility, high reliability, and there are no restrictions on oil content selection or form, which makes it possible to develop a large number of applications.
According to the present invention, the uniformity of the composite particles in the aqueous dispersion can be checked by a simple method at the stage of the intermediate of the oil-in-water emulsion, so that the stability and uniformity of the final emulsion can be ensured. Yield to prevent defective products is significantly improved. Moreover, it is possible to design for that purpose.

When an emulsion is the target product, it can be added to various cosmetics to attach various silicones, which are oils, to hair and skin to give various effects. A large number of existing applications, such as applications that require a coat that requires precision and reproducibility, and coats that require a uniform coat that requires extremely heat resistance, such as a mold release agent for die casting. It is expected to improve and develop new applications.
According to the present invention, an oil-in-water emulsion that ensures stability and uniformity is produced, and the coverage of the silica layer can be controlled, so that a reliable composite particle can be obtained.

When silica works as a functional particle in the case of removing water and isolating composite particles, in the use of conventional plastic reinforcing materials, it is possible to impart a function of reducing moisture absorption by the action of oil, or rubber. In the case of silicone rubber that has been given elasticity or hardened with oil, it can be used as a cosmetic powder that gives a silky feel and has a stretchable feeling because the inside is soft and the outside is hard. Since the variation as a composite particle is small in these applications, the function in the application is improved.
If silica is not a functional particle, when blending silicone rubber particles into various paints and plastics, the performance may be improved due to the good particle size and shape uniformity, or the composite particles may be returned to water as appropriate. A new product form as a kind of dry emulsion, which is to emulsify, is also conceivable.

The fluorine-containing organopolysiloxane emulsion according to the present invention can be in the form of granules or powders by various granulation or powdering techniques. The form of the fluorine-containing organopolysiloxane is not limited, but it is preferably in the form of rubber or resin, that is, in the form of solid at room temperature. In the case of rubber, it is preferable to prepare it as a curable composition such as an addition reaction type and perform curing after forming an emulsion.
The spray-drying method is preferable as the method of granulation or powdering.

Since the fluorine-containing organopolysiloxane emulsion composition according to the present invention can be granulated or powdered, the shape of the granules or powder is fixed and the size variation is small as compared with the method of pulverizing from the form of rubber or resin. , Surface tension is small, intermolecular force is small, heat resistance is high, insulation is high, dielectric constant is high, etc., which are the essential characteristics of fluorine-containing organopolysiloxane. Combined with the powdery state, it is possible to impart performance such as water repellency, oil repellency, heat resistance, cosmetic performance, stain resistance, weather resistance, mold release, long-term stability, insulation or high dielectric constant to the substrate.
In particular, in the surface layer of the silicone rubber particles coated with the fumed silica particles, the network-like surrounding structure of the fumed silica particles or the cohesive force acting between the oily component of the silicone rubber particles before curing and the fumed silica particles causes. A constant interfacial tension works, and as a result, a force that tries to minimize the surface area of the dispersed oil phase works. As a result, the shape of the emulsified silicone rubber particles becomes closer to a true sphere.
The rate of the curing reaction must not be too fast for the silicone rubber particles to be closer to a true sphere. That is, if the curing reaction proceeds while the oil layer distorted by the shearing force tries to return to a spherical shape due to the interfacial tension of the surface layer during emulsification and dispersion, it becomes difficult to obtain the desired sphericity.

Products can be provided as granules or powders for various applications, and handling in various applications is safe and convenient. By blending it into various plastics or the like as granules or powders, the above-mentioned excellent properties can be imparted to the plastics and the like. Alternatively, by blending it with various protective coating agents and cosmetics, it is possible to impart exactly the same effect to the substrate as in the case of film formation.
Furthermore, it is possible to impart characteristics unique to granular or powdery substances, such as strength improvement and silky feeling, to various substrates.
In particular, in the case of cosmetic applications, the fluorine-containing organopolysiloxane is compared with the case where the granular or powdery fluorine-containing organopolysiloxane and the granular or powdery fumed silica are separately applied to hair, skin, etc. Since the emulsion composition can be made into granules or powder, and the fumed silica particles are firmly adhered to the outer surface of the oil droplets, the fumed silica particles are applied in advance, and fluorine is an oil droplet. It is possible to reliably create a situation where the contained organopolysiloxane will be applied later.

Next, the present invention will be described by way of examples. The present invention is not limited thereto. The contents of the fumed silica used in the examples are as follows, and the evaluation method for the oil-in-water emulsion of the fumed silica particles of the present invention and the composition in the comparative example was as follows. ..

<Contents of fumed silica>
The silica used in the examples and comparative examples of the present invention is silica 1 to 3 shown in Table 1, and both are fumed silica (dry silica). The contents are as shown in Table 1.

<Particle size measurement method>
The particle size of the oil-in-water emulsion particles obtained in Examples and Comparative Examples was measured using a laser diffraction / scattering method particle size distribution measuring device (trade name “LS-230”) manufactured by Beckman Coulter, and the average particle size. showed that.

<Stability and uniformity evaluation method>
In the method for evaluating the stability of the oil-in-water emulsion obtained in Examples and Comparative Examples, 30 g of a sample was placed in a 50 ml screw tube, and the presence or absence of sedimentation separation was confirmed after 1 month of storage at room temperature. The presence or absence of creaming was also confirmed for the emulsion. In addition, it was visually confirmed whether there were large particles and whether there was turbidity on the sides, and the uniformity was confirmed.
Evaluation criteria;
⊚: No creaming, sedimentation separation, uniform, ○: Slight creaming, sedimentation separation, very slightly non-uniformity, Δ: Creaming, sedimentation separation, non-uniformity tendency, ×: Creaming, sedimentation separation ,Unevenness.

<Water repellency evaluation method>
The oil-in-water emulsion obtained in Examples and Comparative Examples was diluted 2-fold with water and applied using a bar coater on a glass plate to form a coating film having a thickness of about 30 μm, which was sufficiently air-dried. After that, the contact angle with water was measured as a water repellency evaluation. If the contact angle is 90 degrees or more, the water repellency is good.

<Method for producing aqueous dispersion and oil-in-water emulsion in Examples and Comparative Examples>
In each Example and Comparative Example, an aqueous dispersion was obtained under the prescription amount and preparation conditions shown in Table 2. Further, an oil-in-water emulsion was prepared in the prescribed amount shown in the same table via the aqueous dispersion.
Table 3 shows the evaluation results of the oil-in-water emulsion.

<Example 1>
As a first step, 2.5 g of hydrophilic fumed silica (“silica 1”) and 2.5 g of hydrophobic fumed silica (“silica 2”) were placed in a 500 mL stainless steel beaker. 45 g of deionized water was added thereto, and the mixture was stirred with Ultraturrax at 3,000 rpm for 2 minutes to obtain a silica aqueous dispersion. The shear rate at that time was about 11,000 s ^-1 .
Subsequently, as the second step, 50 g of a fluorine-containing organopolysiloxane having a viscosity of 1000 mPa · s (available from Wacker Chemie (Munich, Germany) under the name AF98 / 1000) is added and stirred at 1,500 rpm for 2 minutes. As a result, a low-viscosity white oil-in-water emulsion was obtained. The shear rate at that time was about 4,600 s ^-1 .

<Example 2>
An aqueous dispersion and a low-viscosity white oil-in-water emulsion were obtained in exactly the same manner as in Example 1 except that 1 g of silica 1 and 4 g of silica 2 were added.

<Example 3>
An aqueous dispersion and a low-viscosity white oil-in-water emulsion were obtained in exactly the same manner as in Example 1 except that 4 g of silica 1 and 1 g of silica 2 were added.

<Example 4>
5 g of partially hydrophobized hydrophilic fumed silica (“silica 3”) was placed in a 500 mL stainless steel beaker. 45 g of deionized water was added thereto, and the mixture was stirred with Ultraturrax at 3,000 rpm for 2 minutes to obtain a silica aqueous dispersion.
Subsequently, 50 g of a fluorine-containing organopolysiloxane having a viscosity of 1000 mPa · s (available from Wacker Chemie (Munich, Germany) under the name AF98 / 1000) was added, and the mixture was stirred at 1,500 rpm for 2 minutes to reduce the content. An oil-in-water emulsion having a white viscosity was obtained.

<Example 5>
An aqueous dispersion and a low-viscosity white oil-in-water emulsion were obtained in exactly the same manner as in Example 1 except that the stirring time in the second step was 1 minute.

<Example 6>
An aqueous dispersion and a low-viscosity white oil-in-water emulsion were obtained in exactly the same manner as in Example 1 except that the stirring in the second step was set to 500 rpm. The shear rate at that time was about 1,500 s ^-1 .

<Example 7>
An aqueous dispersion and a low-viscosity white oil-in-water emulsion were obtained in exactly the same manner as in Example 1 except that the stirring time in the first step was 1 minute.

<Example 8>
The oil-in-water emulsion obtained in Example 1 was diluted 2-fold with water on an iron plate having a smooth surface and a metallic luster without rust to form a film having a film thickness of 30 μm using a bar coater. When this board was exposed to the outdoors for one month, the surface was greatly rusted without the coat, whereas the initial metallic luster was maintained with the coat.

<Example 9>
The oil-in-water emulsion obtained in Example 1 was diluted 2-fold with water on a steel sheet coated with an acrylic melamine resin to form a film having a thickness of 30 μm using a bar coater. When this plate was immersed in water at room temperature for one week, the resin swelled without the coating, whereas with the coating, the initial state of the resin was maintained.

<Example 10>
The oil-in-water emulsion obtained in Example 1 was put into a commercially available UV protection makeup agent at 5%, stirred well, and then diluted 2-fold with water on a glass test piece using a bar coater. It was applied to a thickness of about 30 μm. After immersing this test piece in water at room temperature for 1 hour, the SPF (Sun Protect Factor) was measured. It decreased to 90% and exceeded the preferable level of 80%.

<Comparative Example 1>
5 g of hydrophilic fumed silica (“silica 1”) was placed in a 500 mL stainless steel beaker. 45 g of deionized water was added thereto, and the mixture was stirred with Ultraturrax at 3,000 rpm for 2 minutes to obtain a silica aqueous dispersion.
Subsequently, 50 g of a fluorine-containing organopolysiloxane having a viscosity of 1000 mPa · s (available from Wacker Chemie (Munich, Germany) under the name AF98 / 1000) is added, and the mixture is stirred at 1,500 rpm for 2 minutes to form an emulsion. However, the underwater oil type property was not sufficient.

<Comparative Example 2>
An overall white liquid was obtained in exactly the same manner as in Comparative Example 1 except that 5 g of hydrophobic fumed silica (“silica 2”) was added instead of 5 g of hydrophilic fumed silica (“silica 1”). The oil-in-water type property in a state of being separated into an aqueous phase which is a continuous phase and an oil phase which is a dispersed phase was not sufficient.

<Comparative Example 3>
2.5 g of hydrophilic fumed silica (“silica 1”) and 2.5 g of hydrophobic fumed silica (“silica 2”) were placed in a 500 mL stainless steel beaker. 45 g of deionized water was added thereto, and the mixture was stirred with Ultraturrax at 500 rpm for 2 minutes to obtain a silica aqueous dispersion. The shear rate at that time was about 1,900 s ^-1 .
Subsequently, 50 g of a fluorine-containing organopolysiloxane having a viscosity of 1000 mPa · s (available from Wacker Chemie (Munich, Germany) under the name AF98 / 1000) was added, and the whole was stirred at 1,500 rpm for 2 minutes. A white liquor was obtained, but the oil-in-water properties in a state of being separated into an aqueous phase as a continuous phase and an oil phase as a dispersed phase were not sufficient.

<Comparative Example 4>
As the first step, 50 g of a fluorine-containing organopolysiloxane having a viscosity of 1000 mPa · s (Wacker Chemie AF98 / 1000 was put into a 500 mL stainless steel beaker. 45 g of deionized water was put into this, and 1 using Ultratralux. By stirring at 900 rpm for 2 minutes, an oil-in-water emulsion was obtained. The shear rate at that time was about 5,700 s ^-1 .
Subsequently, as a second step, 2.5 g of hydrophilic fumed silica (“silica 1”) and 2.5 g of hydrophobic fumed silica (“silica 2”) were added and stirred at 3,000 rpm for 2 minutes. The shear rate at that time was about 11,000 s ^-1 .
An entirely white liquid was obtained, but the oil type in water was not sufficient in a state of being separated into an aqueous phase as a continuous phase and an oil phase as a dispersed phase.

<Comparative Example 5>
Hydrophilic fumed silica (“silica 1”) 2.5 g, hydrophobic fumed silica (“silica 2”) 2.5 g, and fluorine-containing organopolysiloxane 50 g (Wacker Chemie AF98 / 1000) with a viscosity of 1000 mPa · s. Simultaneously charged into a 500 mL stainless steel beaker. 45 g of deionized water was charged therein and stirred at 3,000 rpm for 2 minutes using Ultraturrax. The shear rate at that time was about 11,000 s ^-1 .
An entirely white liquid was obtained, but the oil type in water was not sufficient in a state of being separated into an aqueous phase as a continuous phase and an oil phase as a dispersed phase.

<Summary of production results of aqueous dispersion and oil-in-water emulsion>
As shown in Tables 2 and 3, the total number of moles of surface hydrophilic groups in each of the silica particle groups at the stage of the raw material fumed silica and the total number of moles of the surface hydrophobic groups in each of the particle groups. When the ratio of the number of moles to the total number of moles over the particle group was in the range of 26/74 to 74/26, stable aqueous dispersions and oil-in-water emulsions were produced. However, when the molar ratio was 90/10, the aqueous dispersion was stable, but a stable oil-in-water emulsion was not produced. At a molar ratio of 10/90, neither the aqueous dispersion nor the emulsion was stable.
Even at a molar ratio of 50/50, neither the aqueous dispersion nor the emulsion was stable at low shear rates.
When the shear rate was sufficiently high, the variation in the degree of surface hydrophobicity at the secondary aggregation level was sufficiently small, but when the shear rate was not sufficient, the variation was large.
Since the fluorine-containing organopolysiloxane, which is an oil component, was sucked in at a shear rate significantly lower than the shear rate applied during the preparation of the aqueous dispersion, the self-micellar aggregates of the aqueous dispersion remained almost unchanged in the oil-in-water form. It is considered that the emulsion (pickering emulsion) has been transferred.
It was confirmed that a stable emulsion could not be obtained in any of the simultaneous mixing of silica, water and oil, and the mixing of water and oil, and the mixing of silica. It was also confirmed that the main shear may be used for the aqueous dispersion and the auxiliary shear may be used for the emulsion. Based on these, the formation of self-micellar aggregates in the aqueous dispersion is inferred.
It was confirmed that the overall molar ratio and variation fluctuate to ensure the stability of the emulsion depending on the cohesiveness of silica.
Regarding shear, where rearrangement is necessary for the stability of the emulsion, if the shear rate is above a predetermined value, the shear time does not matter, but the shear rate and the shear time are related to the specification adjustment of the composite particles. It was confirmed.
As described above, even when a fluorine-containing organopolysiloxane having super water repellency or super oil repellency is used as an oil component, a fluorine-free organopolysiloxane is added by post-adding the oil component after forming an aqueous dispersion. It has been confirmed that a stable aqueous dispersion and a stable emulsion can be formed under almost the same conditions as (shearing conditions at the time of forming the aqueous dispersion). It is the content to overturn.

<Consideration of the formation of self-micellar aggregates>
(1) In an oil-in-water emulsion from silica, water and oil, a stable oil-in-water emulsion is formed by adding oil after forming an aqueous dispersion of silica and water, and the silica, water and oil are simultaneously formed. The fact that stable oil-in-water emulsion was not formed by adding oil and water first and then adding silica (2) Add oil after forming an aqueous dispersion of silica and water. In this case, it is necessary to apply shear at a predetermined shear rate or higher when forming the aqueous dispersion for the formation of a stable and uniform aqueous dispersion, and oil is added by the stable and uniform aqueous dispersion to produce oil in water. The fact that shearing was not always necessary to form the mold emulsion (3) Regardless of the type of silica and oil as raw materials, adding oil after forming an aqueous dispersion with silica and water. (4) Total number of moles of surface hydrophilic groups in each silica particle group / total number of moles of surface hydrophobic groups in each of the silica particle groups / silica The total number of moles ratio, which is the total number of moles over the particle group, and the average value of the total number of moles ratio, and the number of moles of surface hydrophilic groups and the number of moles of surface hydrophobic groups in each of the secondary particles constituting the silica particle group. Stable emulsion formation is possible by setting two parameters, the difference between the number and the molar ratio, within a predetermined range. In this case, the silica particles are mainly composed of hydrophilic-rich agglomerates. The fact that the expression of thixotropic properties was reduced due to the solubility in water and the fact that the silica particles were mainly composed of hydrophobic-rich aggregates. (5) When the composite particles in the stable oil-in-water emulsion were observed by SEM, The fact that a lump of relatively spherical and uniformly sized particles covers the surface of the oil droplets on the surface of the composite particles (6) In the composite particle group to be formed, the variation in particle size and the like between the composite particle groups is small. That, the fact that the shear rate in the form of the aqueous dispersion affects the specifications of the composite particles From the above facts in the examples, when forming the aqueous dispersion with silica and water, by applying shear at a predetermined shear rate. Due to the high cohesiveness of the fumed silica particles, when the fumed silica particles form a network, they form a surrounding structure that forms a space inside a three-dimensional structure instead of a planar structure, and is hydrophilically rich. Agglomerates that are neither major particles nor hydrophobic rich aggregates are formed. By adjusting the variation in the total number of moles ratio and the total number of moles ratio and adding the oil afterwards regardless of the type of raw material silica and oil, a stable oil-in-water emulsion is formed, so shearing is applied. In doing so, rearrangement and / or orientation within the silica aggregates is induced between the silica aggregates, resulting in high density of hydrophilicity on the outside and hydrophobicity on the inside, self-micellar coagulation during the formation of aqueous dispersions. It is definitely inferred that the aggregate is formed.

The aqueous dispersion of inorganic particles according to the present invention is stable and uniform, and exhibits functions such as thickening and imparting thixotropy, so that reliability is significantly improved in conventional applications such as paints, cosmetics, and modification of various resins. , Functional paints, functional coatings, adhesives, building sealants and other new applications. It can also be used as an intermediate for producing a stable and uniform pickering emulsion.
In addition, the oil-in-water emulsion (pickering emulsion) according to the present invention has extremely high stability and uniformity, and the uniformity can be checked at the intermediate stage regardless of the type of oil content, and the manufacturing method is simple and low cost. Since it can be designed to obtain stable and uniform products, the reliability in conventional applications is greatly improved, and it is highly required for highly functional cosmetic applications, electronic materials, airbags, etc. It can be expected to be applied in new fields that require reliability.
When the composite particles of the oil-in-water emulsion of the present invention are isolated, the stability and uniformity are ensured, so that the composite particles are easy to handle, have little variation in characteristics, and can provide highly reliable composite particles. New applications can be expected in applications and addition to various resins. In addition, since it is possible to add water again to return it to an emulsion, it can be expected to significantly improve the cost of storing the product in an emulsion state and transporting it, which has a great impact on the industrial world.
Since the emulsion of the present invention can give a film, granules or powder shape of a fluorine-containing organopolysiloxane, which was not possible in the past, water repellency, oil repellency, heat resistance, cosmetic performance and protection against the substrate. It can provide stain, weather resistance, mold release, long-term stability, insulation or high dielectric constant. Therefore, it is possible to improve the characteristics in various industrial and general applications such as protective coatings and cosmetic applications, which were impossible or insufficient in the past, and to develop new applications.
Since the use of organic surfactants can be reduced without omitting it, environmental problems associated with it, stable production, existence in the form of stable emulsions, and the fact that organic surfactants are free and can be supplied in an aqueous system make the skin. It is also useful as a cosmetic raw material to be applied directly to the skin and from the viewpoint of hypoallergenicity, and may be used advantageously in many industries.

It is a schematic diagram of a network-like surrounding structure in which oil is surrounded by agglomerates of fumed silica group. In the embodiment, it is a schematic diagram of what kind of aggregate can be formed when the fumed silica particles are dispersed in water, and the size of the aggregate itself is exaggerated for clarity. ..

10 Hydrophobic rich primary aggregate 12 Hydrophobic rich primary aggregate 14 Secondary aggregate 16 Space 18 Network structure 20 Aqueous phase 22 Oil phase 24 Aggregate by fumed silica particle group

Claims (9)

It is a fumed silica particle group in which lower aggregates of the fumed silica particle group form high-level aggregates by non-chemical bonds, and contains a network-like surrounding structure containing oil inside.
The oil content is an organopolysiloxane having an average composition represented by the general formula (1).
R ¹ _a R ² _b SiO _{(4-ab) / 2} (1)
[In formula (1), R ¹ may be the same or different in the molecule, and is a substituted or unsaturated saturated or unsaturated monovalent hydrocarbon group having 1 to 25 carbon atoms, substituted or unsubstituted. Carbon number 6
It is an aromatic group to 30, a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms or a hydrogen atom, and R ² may be the same or different in the molecule, and is saturated or unsaturated with 1 to 25 carbon atoms. A saturated monovalent hydrocarbon group, or an aromatic group having 6 to 30 carbon atoms, in which a hydrogen atom on at least one carbon is substituted with a fluorine atom, and b is a positive non-zero number. a + b is 0.3 or more and less than 2.5, and a / b is 5/95 or more and less than 95/5]
No creaming or sedimentation was observed in the visual evaluation results after 1 month of storage at room temperature.
An oil-in-water emulsion characterized by this. In the network-like surrounding structure, the high-density portion of the lower hydrophilicity-rich aggregate is in contact with the aqueous phase, and the high-density portion of the hydrophobic-rich lower aggregate is in contact with other hydrophobic-rich lower aggregates. The oil-in-water emulsion according to claim 1, which comprises a self-micellar aggregate that forms a space containing oil. The oil-in-water emulsion according to claim 2, wherein in the self-micellar aggregate, the lower aggregates form a network-like structure. A group of fumed silica particles having a secondary aggregation level is prepared by mixing a hydrophobic rich silica raw material obtained by hydrophobizing the surface silanol groups and a hydrophilic rich silica raw material having residual surface silanol groups at a predetermined ratio. Stages and
By adding the prepared fumed silica particle group at the secondary aggregation level to water and shearing at a shear rate of a predetermined value or higher, the lower aggregates of the fumed silica particle group are highly coagulated by non-chemical bonding. At the stage of forming an aqueous dispersion containing a network-like surrounding structure having a space formed inside, which is a group of fumed silica particles forming an aggregate.
It has a step of adding an oil component to form an emulsion in the generated aqueous dispersion.
As a result, the composite particle group in the form of containing oil is contained in the network-like surrounding structure formed by the fumed silica particle group at the secondary aggregation level , and creaming or creaming or creaming is performed in the visual evaluation result after 1 month of storage at room temperature. A method for producing an oil-in-water emulsion, which is characterized in that no sedimentation separation is observed .
A method for producing an oil-in-water emulsion, wherein the oil content is an organopolysiloxane having an average composition represented by the general formula (1).
R ¹ _a R ² _b SiO _{(4-ab) / 2} (1)
[In formula (1), R ¹ may be the same or different in the molecule, and is a substituted or unsaturated saturated or unsaturated monovalent hydrocarbon group having 1 to 25 carbon atoms, substituted or unsubstituted. Carbon number 6
It is an aromatic group to 30, a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms or a hydrogen atom, and R ² may be the same or different in the molecule, and is saturated or unsaturated with 1 to 25 carbon atoms. A saturated monovalent hydrocarbon group, or an aromatic group having 6 to 30 carbon atoms, in which a hydrogen atom on at least one carbon is substituted with a fluorine atom, and b is a positive non-zero number. a + b is 0.3 or more and less than 2.5, and a / b is 5/95 or more and less than 95/5] . Prior to the formation step of the aqueous dispersion, there is a step of blending the fumed silica particle group at the secondary aggregation level and the organic surfactant at a predetermined blending ratio so as to adjust the morphology of the network-like surrounding structure. The method for producing an oil-in-water emulsion according to claim 4. In the network-like surrounding structure, the high-density portion of the lower hydrophilicity-rich aggregate is in contact with the aqueous phase, and the high-density portion of the hydrophobic-rich lower aggregate is in contact with other hydrophobic-rich lower aggregates. The method for producing an oil-in-water emulsion according to claim 4 or 5, which comprises a self-micellar aggregate that forms a space containing oil. The compounding step of the fumed silica particle group at the secondary aggregation level and the organic surfactant is a predetermined compounding ratio so as to adjust the adhesion of the self-micellar aggregate to the oil droplets surrounded by the self-micellar aggregate. The method for producing an oil-in-water emulsion according to claim 6, which comprises a step of determining. The preparatory stage of the fumed silica particle group at the secondary aggregation level is the fumed silica particle group having the number of moles of surface hydrophilic groups in each of the fumed silica particle groups so as to adjust the proportion of self-micellar aggregates. Total number of moles over / total number of moles of surface hydrophobic groups in each of the fumed silica particle groups, which is the total number of moles over the fumed silica particle group, is set as a predetermined range, and the hydrophobic rich silica raw material and hydrophilicity are used. The method for producing an oil-in-water emulsion according to claim 6, which comprises a step of mixing with a rich silica raw material. Granules having a variation in particle size within a predetermined range by evaporating the aqueous phase by a spray-drying method using the oil-in-water emulsion produced by the method for producing an oil-in-water emulsion according to claim 7 or 8. A method for forming a granular material or powder, which further comprises a step of forming the product or powder.

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